Not Applicable.
The invention relates to engine driven pressure washers and more particularly to an engine idle controller for an engine driven pressure washer.
A pressure washer includes an electric motor or an engine driven high pressure liquid pump. Generally, the pump has a water inlet which is connected through a hose to a water main. Optionally, a suitable cleaning solution may be mixed with the water either at the pump or upstream or downstream from the pump. The pump increases pressure of the water or other liquid from a relative low inlet pressure to a significantly higher outlet pressure. The high pressure water is delivered to a wand for directing a water spray at a surface to be cleaned. Normally, the wand includes a manually operated trigger valve for turning the water flow on and off, and a nozzle which shapes the spray pattern and determines the velocity of the high pressure spray. When the valve is closed, the pump can be subjected to a high static load. An unloader valve may be provided for allowing the pump to continue to operate by recirculating the water through the unloader valve back to the inlet to the pump. However, a typical unloader valve may still place a sufficient back load on the pump to cause excess heat buildup and excess wear on the motor and pump. When the pump is driven by an electric motor, a pressure responsive switch may be provided between the pump and the wand for stopping the motor while the water discharge valve is closed to prevent excess wear on the motor and pump, excess heat generation and unnecessary energy consumption. When the water pressure to the wand drops in response to opening the wand trigger valve, the motor is immediately restarted. This approach will not work when a gasoline engine is used to drive the pressure washer pump, since an engine cannot be restarted as quickly as a motor. Consequently, an unloader valve is used with engine driven pressure washers, and the engine and pump are operated against the constant back load of the unloader valve when the trigger valve is closed.
According to the invention, an idle controller is provided for an engine driven pressure washer. Although an engine cannot be stopped and restarted with sufficiently fast response to the operation of a trigger valve, the engine speed can be quickly changed in response to water flow and pressure demands. When the trigger valve on the wand is closed to stop the water spray, the controller senses the cessation of water flow to the wand and moves the engine throttle to an idle position. When the trigger valve is opened, the limited water flow to the wand produced by the idling engine is sufficient for the controller to return the engine to full throttle. The pump may include a small bypass passage connecting the pump inlet and outlet together. The bypass passage is sized to carry the limited water flow produced by the pump when the engine is idling. The passage will not carry the significantly higher water flow from the pump when the engine is operated at full throttle. If desired, the bypass passage can include a valve which is opened by the engine idle controller when the engine is set to idle and is closed by the engine idle controller when the engine is set to full throttle. Alternately, the engine may be provided with a centrifugal clutch which reduces but does not totally eliminate the load from the pump on the idling engine. The engine is sufficiently coupled through the centrifugal clutch to the pump during idle to cause the pump to operate with the trigger valve is opened to produce a sufficient water flow to the wand for operating the idle controller.
Accordingly, it is an object of the invention to provide an engine idle controller for an engine driven pressure washer.
Other objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings.